Venturi vacuum responsive exhaust gas recirculation control system

ABSTRACT

An exhaust gas recirculation control system wherein a vacuum motor responsive to carburetor venturi vacuum varies the loading on a valve controlling air bleed to a vacuum operated servo unit which positions an exhaust gas recirculation control valve so as to provide a recirculation rate proportional to venturi vacuum and engine air consumption.

[ Nov. 27, 1973 United States Patent [191 King [ VENTURI VACUUM RESPONSIVE EXHAUST GAS RECIRCULATION CONTROL SYSTEM Primary ExaminerLaurence M. Goodridge Assistant Examiner-Dennis Toth Attorney-J. L. Carpenter et a1.

[75] Inventor:

Jack B. King, Royal Oak, Mich.

[73] Assignee: General Motors Corporation,

ABSTRACT Detroit, Mich.

22 Filed: May 8, 1972 21 Appl. No.: 250,985

An exhaust gas recirculation control system wherein a vacuum motor responsive to carburetor venturi vacuum varies the loading on a valve controlling air bleed to a vacuum operated servo unit which positions an exhaust gas recirculation control valve so as to provide a recirculation rate proportional to venturi vacuum and engine air'consumption.

6 A A y 1 1 1 1 3m3 222 101 aF A m 9 m 1 1 /n. 3 n" 2 n" 1 m mmh "c "a nae "as L hf C .M Umm ll] 2 8 555 [56] References Cited UNITED STATES PATENTS 2 Claims, 4 Drawing Figures 3,542,004 11/1970 Cornelius........................ 123/119 A Patented Nov. 27, 1973 2 Sheets-Sheet 1 g 5% Q 3 MxC M U 6 W, K w l w .2 Wm Q w z m v Patented Nov. 27, 1973 3,774,583

2 Sheets-Sheet If VENTURI VACUUM RESPONSIVE EXHAUST GAS RECIRCULATION CONTROL SYSTEM This invention relates to exhaust gas recirculation for internal combustion engines and, in particular, to a control for the exhaust gas recirculation valve in a motor vehicle exhaust emission system to provide a recirculation rate proportional to engine air consumption.

One of the methods used to reduce oxides of nitrogen emissions from the exhaust gases in an internal combustion engine is to recirculate a portion of the exhaust gas through the engine air intake upstream of the intake manifold. To achieve a greater reduction in the oxides of nitrogen with minimal deterioration of vehicle drivability, the amount of exhaust gas recirculation should be proportional to engine air consumption throughout the normal operating range of the engine. Additionally, it is desirable to stop recirculation during engine idling and operation at or near wide open throttle.

The present invention provides a control system for exhaust gas recirculation satisfying the above needs. In particular, the system incorporates a first vacuum motor which uses the venturi vacuum signal to provide an output proportional to the engine air consumption. A second vacuum motor fluidly connected to the throttle bore of the carburetor controls the EGR or exhaust gas recirculation valve. At idle, the second vacuum motor experiences minimum vacuum and maintains the valve in the desired closed position. To provide proportional control during normal operation, output of the first vacuum motor is connected by a spring to an air bleed valve in the vacuum line leading to the second vacuum motor. The air bleed valve acts to limit the maximum vacuum in the line and at the second vacuum mojor proportional to venturi signal. At a predetermined air flow rate, corresponding to the desired maximum recirculation rate, the air bleed valve closes, and as the throttle is opened further the vacuum in the throttle bore decreases resulting in a decreasing vacuum at the second vacuum motor. Accordingly, the exhaust gas recirculation valve gradually closes as the throttle bore vacuum decreases. At a second predetermined air flow rate near wide open throttle, the exhaust gas recirculation valve will be completely closed. Accordingly, the system provides flow proportional valve regulation during normal driving while ceasing recirculation during idling and high power demand operation.

The above and other features of the present invention will be apparent to one skilled in the art upon reading the following detailed description, reference being made to the accompanying drawings illustrating a preferred embodiment of the present invention in which:

FIG. 1 is a plan view of a V-8 engine intake manifold containing induction passages and an exhaust crossover passage, the manifold including a carburetor spacer plate containing an exhausj recirculation passage and carrying an exhaust recirculation valve assembly;

FIG. 2 is a transverse sectional view taken generally along line 2-2 of FIG. 1 showing the induction and exhaust crossover passages and the inlet to the exhaust gas recirculation passage in the spacer plate to which a carburetor has been added;

FIG. 3 is an enlarged sectional view taken along line 3-3 of FIG. 1 showing the details of the exhaust gas recirculation control valve, the venturi vacuum responsive vacuum motor including the air bleed valve, and the vacuum connections with the carburetor; and

FIG. 4 is a modified form of the present invention incorporating a single unit having a venturi vacuum responsive motor and an exhaust gas recirculation valve.

Referring to FIGS. 1 and 2, there is shown an intake manifold 10 for a V-8 type internal combustion engine 12. The intake manifold 10 has a pair of vertical primary riser bores 14 and 16 and a pair of secondary riser bores 18 and 20. The riser bores 14 and 18 open to an upper horizontal plenum 22 connected forwardly or leftwardly as viewed in FIG. 1 to a first pair of transverse runners 24 and 26. The riser bores 14, 18 are connected rearwardly or rightwardly as viewed in FIG. 1 to a second pair of transverse runners 28 and 30. In a similar fashion, the riser bores 16 and 20 open to a lower horizontal plenum 32 which are connected forwardly to a third pair of transverse runners 34, 36. The riser bores 16, 20 are rearwardly connected to a fourth pair of transverse runners 38 and 40.

An exhaust crossover passage 42 extends transversely beneath the plenums 22, 32 between ports 44, 46. During engine warmup, the exhaust gases are routed through the exhaust crossover passage 42 by a conventional temperature responsive valve to promote rapid heating of the intake manifold.

A carburetor spacer plate 48 is centrally secured on the intake manifold 10and has primary riser bores 50, 52 respectively registering with riser bores 14, 16. The spacer plate 48 has secondary riser bores 54, 56 respectively registering with riser bores 18, 20. A carburetor 60 is mounted on the spacer plate 48 and has primary throttle bores 62, 64 which register respectively with primary riser bores 50, 52. The throttle bores 62, 64 include venturis 66, 68 respectively. The carburetor 60 additionally has secondary throttle bores (not shown) which register with the secondary riser bores 54, 56 of the spacer plate 48.

A vertical port 70 is slightly spaced from the secondary riser bore 56 and leads upwardly from the exhaust crossover passage 42. The port 70 fluidly connects with a horizontal runner 72 of an exhaust gas recirculation passage formed in the carburetor spacer plate 48. The runner 72 leads through an exhaust gas recirculation or EGR valve to a second horizontal runner 82 of the recirculation passage. The second runner 82 has a pair of branches 84, 86 which lead to the primary riser bores 50, 52 in the spacer plate 48.

identical in construction to that disclosed in the pendn anpli afiqn 9f Edwar Day nd E e Ranfh U.S. Pat. Ser. No. 90,399, filed on Nov. 17, 1970 and entitled Exhaust Gas Recirculation. The present valve functions in the .same manner and will be described primarily with reference to its operation in the instant system.

The valve 80 generally comprises a motor housing 90 having a circular diaphragm 92 dividing the former into a vacuum chamber 94 and an atmosphere chamber 96. A downwardly projecting valve stem 98 is centrally attached to the diaphragm 92. The valve member 100 is attached to the valve stem 98 and has a conical pintle which cooperates with a circular valve eat 102 mounted on a valve body 104 to restrict the flow of exhaust gases from the runner 72 through an intermediate chamber 106 to the second runner 82. The housing 90 and the valve body 104 are suitably mounted on the spacer plate 48. A coiled spring 108 disposed in the vacuum chamber 94 serves to normally bias the diaphragm 92, the valve stem 98, and the valve member 100 to a closed position.

During engine operation, the flow conditions in the venturi 68 of the throttle bore 64, produce a vacuum signal proportional to engine air consumption. In the present invention, this vacuum signal is used to control the opening and closing of the valve 100. More particularly, the primary throttle bores 62 and 64 include throttle plates 110, 112, which are controlled by a suitable throttle linkage, the throttle plate 112 being illustrated in the closed position in FIG. 3. A port 120 is formed in the carburetor and communicates with the venturi 68. A vacuum conduit 122 fluidly connects the port 120 with a venturi signal responsive vacuum motor 124. A port 126 communicates with throttle bore 64 slightly upstream of the throttle plate 112 when the latter is in the closed position. The port 126 is fluidly connected to an air bleed valve 130 and the EGR valve 80 by vacuum lines 132, 134 which together with the vacuum motor 124 form a control system for recirculation of exhaust gases.

During operation of the engine at closed throttle, the air flow through the venturi 68 and the throttle bore 64 produces a minimal vacuum. As the throttle is progressively opened and as the edge of the throttle plate 112 traverses the port 126, a maximum vacuum condition will exist in lines 132, and 134 and at port 126. As the air flow through the venturi 68 progressively increases, the vacuum signal increases while the vacuum at port 126 progressively decreases. These vacuum conditions will be utilized in the hereinafter described manner to provide three modes of control for the valve 80.

The vacuum motor 124 comprises a cover 140 and a base 142 between which a flexible diaphragm 144 is disposed. The diaphragm 144 and the cover 140 cooperate to define a vacuum chamber 146. The vacuum conduit 122 is connected to a port 148 in the cover 148 to connect the chamber 146 to vacuum conditions at the venturi 68. A stem 150 is centrally connected to the diaphragm 144 and moves axially in accordance with movement thereof. A coil spring 152 is interposed between base 142 and a stop plate 154 adjustably carried on the stem 150. The spring 152 normally biases the stem 150 to the right or minimum output position.

The air bleed valve 130 is mounted on a plate 160 connected to the base plate 142 by studs 162. The air bleed valve 130 includes housing sections 166, 168 defining an intermediate vacuum chamber 170 in lines 132, 134. The section 166 includes ports 172, 174 which are respectively connected to vacuum lines 132, 134. in this manner, vacuum conditions at the throttle bore 64 are transmitted through intermediate chamber 170 to the chamber 94. The rear section 168 includes a conical valve seat 180 in which a conical head of an air bleed valve member 184 is seated. The shank of the air bleed valve member 184 is connected to the stem 150 by an extension spring 186. The initial preloading of the spring 186 may be varied by adjustment of an adjusting screw 190 which pivots the air bleed valve 130 against the biasing of the spring 186 and by adjustment of the preloading of the spring 152.

The chamber 170 will experience vacuum conditions in accordance with the vacuum at the port 126. The pressure differential on either side of the valve 184 will act against the loading of the spring 186 to govern the opening and closing of the valve 130. Inasmuch as the loading on the spring 186, after initial setting of the preloading, will be determined by the position of stem 150 of motor 124, the air bleed into chamber 170 will be inversely proportional to the venturi signal and engine air consumption. Accordingly, the loading on the spring 186 can be coordinated with diaphragm movement 144 to control the air bleed into chamber 170.

The amount of air bleed can then be used to control maximum and minimum vacuum conditions in chamber 94 of the EGR valve 80. At minimum vacuum, the valve would be closed. At idle, for instance, the vacuum at the port 126 will be minimal as will the engine air consumption or venturi vacuum at the port 120. Accordingly, the output of the motor 124 is minimal and the force of spring 186 is at its lowest value. This result in maximum air bleed through the valve 184 and the vacuum in lines 132, 134 will be the lowest. Under these vacuum conditions, the spring 108 is selected to bias the valve 100 fully closed. As the throttle 112 begins to open, the vacuum in line 132 will abruptly increase to a maximum value while the air flow will slightly increase so that the loading on the valve 184 is still essentially at the minimum and the air bleed is at a maximum. The air bleed under these conditions is selected to establish a vacuum in chamber 170 as transmitted through lines 134 to chamber 94 which acts to balance the biasing of spring 108. Thereafter, as the throttle opens; the vacuum in line 132 decreases while the air flow signal at port increases. This increases the output of motor 124, extends the spring 186 and decreases the air bleed across valve member 184. Inasmuch as the vacuum at port 120 increases at a faster rate than the rate of decrease at port 126, the transmitted vacuum to the chamber 94 will increase thereby progressively opening the EGR valve 100. At the air flow rate where maximum recirculation is desired, the air valve bleed is selected to be the lowest such that the spring 186 holds the valve member 184 closed against the pressure differential. Under these conditions, the pressure differential on the diaphragm .92 is greatest, the opening of valve 100 is at a maximum, and the flow of exhaust gases from runner 72 to runner 82 is at a maximum. As the throttle opening increases, the vacuum in line 132 decreases, the closing force on valve member 184 increases and the vacuum in chamber 94 gradually decreases thereby resulting in a closing movement of the valve 80. At or near wide open throttle, where vacuum at port 126 is minimal, the vacuum in chamber 94 is minimal and the spring 108 biases valve member 100 to the closed position.

This system thus provides three distinct operating modes for the EGR valve 80. First, the valve 80 will be fully closed during idling. Second, as the throttle opening progressively increases, the valve 80 will gradually open to a predetermined amount and provide an exhaust gas recirculation flow rate proportional to engine air consumption. Third, after the desired maximum flow, the valve 80 will gradually close until shut at wide open throttle.

Referring to FIG. 4, there is shown an alternate form of the invention wherein the exhaust gas recirculation valve, the venturi vacuum responsive motor, and the air bleed motor are integrated into a single unit. More particularly, a multiple purpose control valve 200 comprises a housing having an upper section 202 and a lower section 204. A pair of diaphragms 206, 208 are positioned on either side of a ring member 210. The diaphragms 206, 208, the ring member 210, and the upper section 202 are secured in spaced relationship to the lower section 204 by an inwardly turned flange 212. The diaphragm 206 and the upper section 202 define a first vacuum chamber 214. The chamber 214 is fluidly connected to the poart 120 of the carburetor by vacuum line 122 via port 216. The diaphragms 206, 208 and the ring 210 define an intermediate chamber 218 exposed to atmosphere at port 222. The lower section 204 and the diaphragm 208 define a second vacuum chamber 224 directly fluidly connected to intake manifold vacuum by line 132 via port 226.

A valve stem 230 carried by the diaphragm 208 includes a conical valve member 232 which cooperates with a cylindrical valve seat 234 to control the flow of exhaust gases therepast. A coil spring 236 in chamber 224 biases the valve stem 230 and the valve member 232 to the open position. An internal axial passage and a radial passage at the upper section of the valve stem 230 define an air bleed passage 238. A valve member 240 carried by the diaphragm 206 includes a head section 242 which seats in the upper portion of the passage 238 to control the passage of air therethrough. A coil spring 244 in the chamber 214 downwardly biases the diaphragm 206 to normally seat the head 242 in the passage 238.

During operation of the engine at idle, the springs 236, 244 cooperate to seat the valve member 242 in the passage 238 and the high vacuum in chamber 224 draws the diaphragm 208 to its lower closed position. As the air flow through the venturi 68 increases, the signal through the line 122 to the chamber 214 increases and the diaphragm 206 will tend to move upwardly against the bias of spring 244. Under these conditions, the valve 242 will be unseated and air will bleed into chamber 224 and diaphragm 208 will move upwardly until equilbrium is established and a valve opening for valve member 232 is achieved in proportion to the engine air consumption. As the air flow through the venturi 68 increases as throttle plate 112 moves to the fully open position, the vacuum in chamber 214 progressively increases and the valve will move steadily upward as described above. This upward movement will continue until such time as the stop plate 250, axially spaced from the valve member 232, engages the lower edge of valve seat 234 and exhaust gas recirculation is stopped. In this form, the travel of the valve member 232 as a function of venturi signal and manifold vacuum is unidirectional.

Although only two forms of this invention have been shown and described, other forms will be readily apparent to those skilled in the art. Therefore, it is not intended to limit the scope of this invention by the embodiments selected for the purpose of this disclosure but only by the claims which follow.

What is claimed is:

1. In an internal combustion engine having an intake manifold having an exhaust crossover passage through which exhaust gases flow, an exhaust gas recirculation passage fluidly connecting the intake manifold and the exhaust crossover passage, a carburetor fluidly connected with the intake manifold, said carburetor having a venturi section with a vacuum signal proportional to engine air consumption and a' throttle bore with a varying vacuum signal having a movable throttle plate; an

' a first vacuum motor having a first diaphragm defining exhaust gas recirculation control system, comprising: a first valve in the recirculation passage, said first valve including a first valve member movable between a maximum opening and a minimum opening with respect to said recirculation passage to restrict flow of exhaust gases therethrough; a first vacuum motor having a first diaphragm means defining a first vacuum chamber; means connecting said first valve member to said first diaphragm means for moving the former between said minimum and maximum openings in accordance with applied vacuum in said first vacuum chamber; first conduit means fluidly connecting the throttle bore with said first vacuum chamber; a second valve associated with said first conduit means, said second valve movable between a first position for admitting air into said first conduit means to reduce the vacuum therein and movable to a second position for preventing the flow of air to said first conduit means, said second valve being biased to said first position by the pressure differential thereacross between atmosphere and vacuum in said first conduit means; a second vacuum motor having second diaphragm means defining a second vacuum chamber; output means connected to said second diaphragm means; second conduit means fluidly connecting the venturi section with said second vacuum chamber whereby said output means moves in accordance with vacuum conditions at said venturi section; yieldable means connecting said output means and said second valve for biasing the latter against the pressure differential in accordance with applied vacuum at said second vacuum chamber, the arrangement being such that the greatest air flow past said second valve is at the lowest applied vacuum in said second vacuum chamber and the applied vacuum in said first vacuum chamber is lowest such that said first valve moves to said minimum opening position, said venturi vacuum signal increasing and said throttle bore signal decreasing upon increasing throttle plate opening whereby the pressure differential decreases and the applied vacuum at said second vacuum chamber increases such that said air flow past said second valve is reduced and the vacuum at said first vacuum chamber increases thereby causing said first valve to move to said maximum opening position at an opening rate proportional to engine air consumption.

2. An internal combustion engine having an intake manifold; a pair of spaced exhaust manifolds for discharging exhaust gases; an exhaust crossover passage in said intake manifold fluidly connecting said exhaust manifolds and defining the flow path for said exhaust gases; an exhaust gas recirculation passage connecting the intake manifold and the exhaust crossover passage; a carburetor associated with the intake manifold, said carburetor having a venturi section with a vacuum signal proportional to engine air consumption and a throttle bore with a varying vacuum signal and having a throttle plate movable therein between an open position and a closed position; an exhaust gas recirculation valve in the recirculation passage, said recirculation valve having an aperture and valve member movable with respect to said aperture to restrict flow of exhaust gases therethrough to thereby control the flow of exhaust gases between said exhaust crossover passage and said intake manifold, said valve member movable between a fully open position and a fully closed position;

a first vacuum chamber; means connecting said valve member to said first diaphragm whereby the former moves between said positions in accordance with applied vacuum in said first vacuum chamber; a first vacuum line fluidly connecting said throttle bore with said first vacuum chamber upstream of the throttle plate when the latter is in said closed position; a second vacuum motor having a second diaphragm defining a second vacuum chamber; an output shaft connected to said second diaphragm; a second vacuum line fluidly connecting the venturi section with said second vacuum chamber whereby said output shaft moves in accordance with vacuum conditions at said venturi sec tion and said second vacuum chamber; an air bleed valve in said first vacuum line, said air bleed valve having a valve movable between a first position for admitting air to said first vacuum line to reduce the applied vacuum therein and movable to a second position wherein the flow or air to said first vacuum line is prevented; a spring yieldingly connecting said output shaft and said valve member and normally biasing said air valve to said second position against the pressure differential thereacross between atmosphere and said first vacuum line, said venturi vacuum signal increasing and said throttle bore vacuum signal decreasing as said throttle plate moves to the open position such that second vacuum motor and spring increasingly opposes said pressure differential and said valve moves to said fully open position at an opening rate proportional to engine air consumption. 

1. In an internal combustion engine having an intake manifold having an exhaust crossover passage through which exhaust gases flow, an exhaust gas recirculation passage fluidly connecting the intake manifold and the exhaust crossover passage, a carburetor fluidly connected with the intake manifold, said carburetor having a venturi section with a vacuum signal proportional to engine air consumption and a throttle bore with a varying vacuum signal having a movable throttle plate; an exhaust gas recirculation control system, comprising: a first valve in the recirculation passage, said first valve including a first valve member movable between a maximum opening and a minimum opening with respect to said recirculation passage to restrict flow of exhaust gases therethrough; a first vacuum motor having a first diaphragm means defining a first vacuum chamber; means connecting said first valve member to said first diaphragm means for moving the former between said minimum and maximum openings in accordance with applied vacuum in said first vacuum chamber; first conduit means fluidly connecting the throttle bore with said first vacuum chamber; a second valve associated with said first conduit means, said second valve movable between a first position for admitting air into said first conduit means to reduce the vacuum therein and movable to a second position for preventing the flow of air to said first conduit means, said second valve being biased to said first position by the pressure differential thereacross between atmosphere and vacuum in said first conduit means; a second vacuum motor having second diaphragm means defining a second vacuum chamber; output means connected to said second diaphragm means; second conduit means fluidly connecting the venturi section with said second vacuum chamber whereby said output means moves in accordance with vacuum conditions at said venturi section; yieldable means connecting said output means and said second valve for biasing the latter against the pressure differential in accordance with applied vacuum at said second vacuum chamber, the arrangement being such that the greatest air flow past said second valve is at the lowest applied vacuum in said second vacuum chamber and the applied vacuum in said first vacuum chamber is lowest sucH that said first valve moves to said minimum opening position, said venturi vacuum signal increasing and said throttle bore signal decreasing upon increasing throttle plate opening whereby the pressure differential decreases and the applied vacuum at said second vacuum chamber increases such that said air flow past said second valve is reduced and the vacuum at said first vacuum chamber increases thereby causing said first valve to move to said maximum opening position at an opening rate proportional to engine air consumption.
 2. An internal combustion engine having an intake manifold; a pair of spaced exhaust manifolds for discharging exhaust gases; an exhaust crossover passage in said intake manifold fluidly connecting said exhaust manifolds and defining the flow path for said exhaust gases; an exhaust gas recirculation passage connecting the intake manifold and the exhaust crossover passage; a carburetor associated with the intake manifold, said carburetor having a venturi section with a vacuum signal proportional to engine air consumption and a throttle bore with a varying vacuum signal and having a throttle plate movable therein between an open position and a closed position; an exhaust gas recirculation valve in the recirculation passage, said recirculation valve having an aperture and valve member movable with respect to said aperture to restrict flow of exhaust gases therethrough to thereby control the flow of exhaust gases between said exhaust crossover passage and said intake manifold, said valve member movable between a fully open position and a fully closed position; a first vacuum motor having a first diaphragm defining a first vacuum chamber; means connecting said valve member to said first diaphragm whereby the former moves between said positions in accordance with applied vacuum in said first vacuum chamber; a first vacuum line fluidly connecting said throttle bore with said first vacuum chamber upstream of the throttle plate when the latter is in said closed position; a second vacuum motor having a second diaphragm defining a second vacuum chamber; an output shaft connected to said second diaphragm; a second vacuum line fluidly connecting the venturi section with said second vacuum chamber whereby said output shaft moves in accordance with vacuum conditions at said venturi section and said second vacuum chamber; an air bleed valve in said first vacuum line, said air bleed valve having a valve movable between a first position for admitting air to said first vacuum line to reduce the applied vacuum therein and movable to a second position wherein the flow or air to said first vacuum line is prevented; a spring yieldingly connecting said output shaft and said valve member and normally biasing said air valve to said second position against the pressure differential thereacross between atmosphere and said first vacuum line, said venturi vacuum signal increasing and said throttle bore vacuum signal decreasing as said throttle plate moves to the open position such that second vacuum motor and spring increasingly opposes said pressure differential and said valve moves to said fully open position at an opening rate proportional to engine air consumption. 